Re: [boost] [Multiprecision] Benchmarking

Subject: Re: [boost] [Multiprecision] Benchmarking
From: John Maddock (boost.regex_at_[hidden])
Date: 2012-06-15 13:59:32

> My test code is here:  http://chezphil.org/tmp/boost_mp_review.tbz2

Just a couple of updates:

1) Your test code doesn't actually test fixed-width integer types anywhere 
as you have:

#ifdef USE_MP_INTN_NOET
  typedef int64_t i64;
  typedef boost::multiprecision::mp_number< 
boost::multiprecision::cpp_int_backend<>, false> i128;
#endif

Should be:

#ifdef USE_MP_INTN_NOET
  typedef int64_t i64;
  typedef boost::multiprecision::mp_number< 
boost::multiprecision::cpp_int_backend<128, true, void>, false> i128;
#endif

Of course the types are pretty similar, and it only saves a few percent - 
relative times on Win32 were:

Your custom int128 1.9.
mp_int128               2.7.
cpp_int (no ET's)     3.2.

2) Some more comparisons with gmp shows expression templates help much more 
in that case:

proposed mpz_int                  100
proposed mpz_int (no ET's)   143
GMP's mpz_class [1]            140

Cheers, John.

1) With apologies to Marc Glisse I used the last released mpz_class, still 
haven't looked at his improvements in GMP development :-(